the SecuredOnboardingService.verify() call hides the upstream error message

[oliverrahner]

Is your feature request related to a problem? Please describe.
When a server side error happens in the SecuredOnboardingService.verify() call, the exception is created without taking into account the upstream error message present in the response body.

Describe the solution you'd like
It should be handled in the same way as in SecuredOnboardingService.onboard(), which includes the upstream error in the exception message.

[saschadoemer]

@oliverrahner does the result have the same format as the onboard error has?

{
  "error": {
    "code": "0110",
    "message": "Signing header is invalid, the request has timedout, or UTCTimestamp is not provided",
    "target": "",
    "details": []
  }
}

The documentation does not have a clear statement to the format (https://docs.agrirouter.com/agrirouter-interface-documentation/latest/integration/onboarding.html#verification-result).

I would assume, that it is the same layout, therefore, see the PR and leave a review. If it is not the case, please let me know.

See #141 as implementation proposal.